1. Technical Field
The invention relates to a radio communication system with a stationary radio device and a mobile radio device.
The invention also relates to a mobile radio device and a stationary radio device for such a radio system as well as to a method for setting up a radio link with such a radio communication system.
2. Discussion of Related Art
A conventional radio communication system with a stationary radio device and a mobile radio device, both of which exchanging radio signals via a radio link, is known from the book "The GSM System for Mobile Communications" which was privately published in 1992 by the authors M. Mouly and M. -B. Pautet in Palaiseau, France. The radio communication system described in the book is the public mobile radio system "Global System for Mobile Communications" (abbreviated GSM) whose technical components comply with the standard "GSM" with the same name. According to this standard, there is provided a radio protocol governing the exchange of radio signals via the radio link between the stationary radio devices--also referred to as base stations- and the mobile radio devices--also referred to as mobile stations. The book by M. Mouly and M. -B. Pautet describes on pp. 192-193 in chapter 4.1.3.1 that the radio channels FCCH (Frequency Correction CHannel) and SCH (Synchronization CHannel) are provided for the base station, on which channels only the base station is allowed to transmit. These radio channels FCCH and SCH are adapted to transmit signaling data in the downward direction and are therefore also referred to as "downlink channel". This book also describes that the radio channel RACH (Random Access CHannel) is provided for the mobile station, on which channel only the mobile station is allowed to transmit. This radio channel RACH is adapted to transmit signaling data in the upward direction and is therefore also referred to as "uplink channel".
In summary, a radio communication system is known which includes a stationary radio device (base station) and a mobile radio device (mobile station), both of which exchange radio signals with each other via a radio link according to a predetermined radio protocol, wherein first radio signals are provided on the channels FCCH and SCH exclusively for transmission by the stationary radio device and second radio signals are provided on the channel RACH exclusively for transmission by the mobile radio device.
A design of a new radio communication system should be based as much as possible on already existing technology in order to save development costs. If the design of a new radio communication system were based on the commonly used GSM mobile radio technology, then the following problems would have to be solved: the new radio communication system and the existing GSM mobile radio systems could interfere with each other due to radio interference problems. The new radio communication system could then only be used in such areas which are not yet serviced by a GSM mobile radio system. Alternately, a radio communication system would have to be based on a completely new design.
EP-A-268 375 proposes to create a new cellular radio system which could be used as a private radio communication system, by providing the base stations with a scanning receiver in conjunction with a completely new radio protocol. The so-called DECT radio system (Digital Enhanced Cordless Telephone) is essentially such a novel radio system which, however, necessitated extensive new developments.